This invention relates to improvements in electrosurgical instruments for and cutting biological tissue. In particular, the invention relates to a device for enhancing the safety and efficiency of a hand-operated electrosurgical pencil which is used in conjunction with a flow of inert gas to provide electrosurgical cutting and to an improved method for performing electrosurgical operations. The invention is also concerned with an improved electrosurgical apparatus with limited current leakage for use with the said device.
Electrosurgical fulguration comprises the application of electric sparking to biological tissue, for example, human flesh or the tissue of internal organs, without significant cutting. The sparking is produced by bursts of radio-frequency electrical energy generated from an appropriate electrosurgical generator. Generally, fulguration is used to dehydrate, shrink, necrose or char the tissue, which operations are primarily to stop bleeding and oozing, or otherwise to seal the tissue. These operations are generically embraced by the term "Coagulation". Electrosurgical cutting comprises electric sparking to tissue with a cutting effect.
As used herein the term "electrosurgical pencil" is intended to mean an instrument comprising a handpiece to which is attached an electrode (the "active electrode"), which may be detachable or fixed. The pencil may be operated by a handswitch or a foot switch. The active electrode is an electrically conducting element which is usually elongated and may be in the form of a thin flat blade with a pointed or rounded distal end, or an elongated narrow cylindrical needle which may be solid or hollow with a flat, rounded, pointed or slanted distal end. Typically electrodes are known in the art as blade electrodes, loop or snare electrodes, needle electrodes and ball electrodes.
An electrosurgical pencil may be used for coagulation or cutting, or when the cutting is accompanied by hemostasis, by cutting and coagulation. The device of the present invention may be used to enhance both coagulation and cutting modes, as hereinafter described.
The handpiece of the pencil is connected to a suitable electrosurgical generator which generates the high frequency electrical energy necessary for the operation of the electrosurgical pencil. An electrosurgical generator suitable for use with electrosurgical electrodes and pencils is disclosed in U.S. Pat. No. 3,699,967, the disclosure of which is incorporated herein by reference. When an operation is performed on a patient with an electrosurgical pencil, electrical energy from the electrosurgical generator is conducted through the active electrode to the tissue at the site of the operation and then through the patient to a return electrode, placed at a convenient place on the patient's body, from whence it is returned via a patient pad or plate made of conductive material to the generator. A suitable circuit is illustrated schematically in U.S. Pat. No. 3,699,967.
The term "electrode" when used herein will generally refer to the active electrode.
The use of a stream of inert gas in conjunction with an electrosurgical electrode is known in the art. Thus, U.S. Pat. No. 4,060,088 (Morrison et al) discloses an electrosurgical method and apparatus for coagulating tissue by fulguration which involves establishing an electrical discharge in an inert gas by flowing said gas through a tubular electrode to which high-frequency electrical energy is applied.
U.S. Pat. No. 4,040,426 (Morrison) which is related to U.S. Pat. No. 4,060,088, discloses a method and apparatus wherein the inert gas flow is disposed adjacent the end of an active electrode to produce a primary electrical discharge in the gas and the apparatus includes a second electrode, electrically isolated from any source of biasing potential, which facilitates the establishment of an auxiliary electrical discharge from an electrostatic charge generated by the inert gas.
A third related U.S. Pat. No. 4,057,064 (Morrison et al) also discloses a method and apparatus for producing coagulation of tissue involving the use of a flow of inert gas and an active electrode.
The present invention provides improvements over the techniques disclosed in the above-mentioned Morrison patents, but since the basic concept of initiating an electrical discharge in an inert gas flow and the general circuitry for carrying out the procedure is a starting point for the apparatus and method of the present invention, the disclosure in each and all of the Morrison patents is incorporated herein by reference.
U.S. Pat. No. 4,781,175 discloses an electrosurgical technique for achieving coagulation involving conducting a predetermined ionizable gas not containing oxygen in a jet to tissue and conducting electrical radio-frequency energy in ionized conductible pathways in the gas jet.
Certain disadvantages present in commercially available units are overcome by the device and apparatus of the present invention.
Surprisingly, it has now been found that if at least one stream or jet of filtered inert gas is directed at a specific predetermined angle to impinge on the electrode of an electrosurgical pencil at or near the tip thereof in a device as hereinafter described the safety and efficiency of the pencil is enhanced. The pencil may be used both for cutting and coagulation, and can be made completely hand-operable; thereby increasing safety and flexibility.
U.S. patent application Ser. No. 07/494,249 (U.S. Pat. No. 5,088,997) describes and claims device for enhancing the safety and efficiency of a hand-operated electrosurgical pencil having an electrode with a distal end defining a tip for cutting or coagulating biological tissue, which device comprises a nose piece having a central axis and a hollow portion extending longitudinally about said axis, which hollow portion is adapted to accommodate said electrode, said nose piece containing conduit means defining at least one pathway for gas, which at least one pathway is disposed at an angle to said central axis so that gas passing therethrough impinges obliquely on said electrode at or near to the tip thereof and means for passing inert gas at a predetermined pressure and flow rate through said at least one pathway.
The configuration of the conduit means provides an angle between the gas pathway and the central axis of the nose piece within the range of about 5.degree. to 30.degree., preferably 12.degree., which corresponds to the angle at which the gas impinges on the electrode.